Safer Badgers - Exposure Notifications

How does the exposure notification feature work in Safer Badgers? Why does it ask for location access?

Safer Badgers App: How COVID-19 Exposure Notification Works

  1. Kyla and Derrick study in the library, not realizing they’re within exposure range for a significant time.
  2. Because they’re both using the Exposure Notification feature, their phones swap anonymous Bluetooth tokens.
    Tokens are randomly generated every few minutes and cannot be traced to any individual or phone. There is no GPS location tracking in the app.
  3. A few days later, Derrick receives test results from University Health Services in his app, and learns he’s positive for COVID-19. Because Derrick tested positive, the app sends tokens from the past 14 days to a secure database.
  4. Kyla’s phone routinely downloads the encrypted tokens of people who tested positive from the secure database.
  5. Kyla’s most recent download contains a match with a token from someone she was recently near.
  6. Because of this match, Kyla gets an exposure notification, letting her know she may have been exposed to someone who tested positive.
  7. Kyla’s app advises her to get tested.


To participate in exposure notification, you must:

  1. Enable the Exposure Notification feature during the app setup or in the Settings menu
  2. Allow Safer Badgers to use Bluetooth and location services when prompted
  3. Allow Safer Badgers to display notifications

Safer Badgers generates local notifications to keep the Bluetooth scanning system engaged while your phone is locked or while exposure notification is working in the background. Your iOS device may display a notification that says "Checking for exposures..." while exposure notifications are enabled:

iOS Exposure notification system checking notification message

Depending on your Android version and settings, enabling exposure notification may add an icon to your status bar to indicate it's running in the background.

How do I know that Exposure Notification is working?

Your device will tell you when Exposure Notification is running. On iPhone, an alert message is displayed periodically that says "Checking for Exposures" when the Exposure Notification functionality is enabled. On Android, the notification screen says "Privacy-preserving contact tracing is currently running."

Our system analytics tell us that Exposure Notifications are being reported anonymously to campus-based users of Safer Badgers.

What distance and time constitutes a "contact" for Exposure Notification?

Exposure Notification is triggered only by a contact that is considered a likely risk. Not every person you are near will be evaluated to determine exposure risk. Proximity is initially set as 2 continuous hours within 10 feet.
Safer Badgers' Exposure Notification feature is not a form of contact tracing. University Health Services (UHS) at UW-Madison provides contact tracing for all positive cases of those affiliated with UW-Madison.

Close contacts of confirmed cases will be notified by secure message in their MyUHS account. MyUHS will send an email or text alerting the person that there is a secure message in their MyUHS account. Individuals who have a COVID-19 infection are interviewed by public health personnel to find out the names of their recent contacts. Those contacts are then interviewed by the contact tracing personnel and given medical guidance.

Why does Safer Badgers need to access my location?

We are not using any location information in Safer Badgers. It's not stored, nor is it sent off the device. iOS and Android require Safer Badgers to ask for location services permissions to use Bluetooth in exposure notifications.

Read the Safer Badgers Privacy Notice.


Additional Help

For frequently asked questions please see: Covid-19 Response FAQs

For more information on the COVID-19 measures on campus, please see COVID-19 Response.

For more information on Safer Badgers, please see Safer Badgers.

If you have further questions or concerns, please contact the UW-Madison COVID-19 Assistance Line at (608) 262-7777.

See Also:




Keywords:app badge badger badgerbadge badgers bluetooth contact coronavirus covid covid19 covid-19 distance exposure gps location low notification pandemic permission permissions privacy safe safebadger safebadgers safer saferbadger saferbadgers tracing tracking, system checking   Doc ID:107312
Owner:Dana G.Group:Safer Badgers
Created:2020-11-19 18:54 CDTUpdated:2021-03-18 18:57 CDT
Sites:DoIT Help Desk, Safer Badgers
Feedback:  3   2